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Old 20th Jan 2020, 8:18 pm   #21
Greycon
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Default Re: 12" P4 Phospher CRT

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Originally Posted by linescan87 View Post
I'll could help you out with this for some beer tokens, feel free to PM me.
Hi John Joe!
Terminal arrived in one piece. I spent the weekend cleaning it all up, keyobard disassembly, electrical contact cleaner, cleaned the PCB on both sides, checked the CAPs as best as I can. In short, it's working very well.

One minor annoyance, the image seems to jitter over and back by a millimeter or so. It's not the end of the world , but if you have any clue what might be causing it, i'd love to know!
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Old 20th Jan 2020, 8:46 pm   #22
linescan87
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Default Re: 12" P4 Phospher CRT

Could be a line sync issue, possibly caused by poor electrolytic caps. Great news that the CRT is ok.
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Old 20th Jan 2020, 8:55 pm   #23
dragonser
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Default Re: 12" P4 Phospher CRT

HI,
I think I had some strange problems maybe similar to the above ? and found that the switch that selects 50 or 60 hz had been set to 60hz...
but changing the caps carefully might well be a good idea...
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Old 21st Jan 2020, 6:43 pm   #24
Greycon
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Default Re: 12" P4 Phospher CRT

@linescan87 @dragonser I am using a decent 220V to 115V stepdown transformer unit. I changed the linesync DIP in the terminal switch to 50Hz and the cursor started rolling up the screen, so I assume the stepdown transformer unit changes the line frequency to 60hz, but I will check that later.

I can live with it, it's pretty minor, but I'm just curious as to how I might debug it. (I have a good scope and the full schematics for the ADM.)
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Old 21st Jan 2020, 8:19 pm   #25
kan_turk
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Default Re: 12" P4 Phospher CRT

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Originally Posted by Greycon View Post
@linescan87 @dragonser I am using a decent 220V to 115V stepdown transformer unit. I changed the linesync DIP in the terminal switch to 50Hz and the cursor started rolling up the screen, so I assume the stepdown transformer unit changes the line frequency to 60hz, but I will check that later.

I can live with it, it's pretty minor, but I'm just curious as to how I might debug it. (I have a good scope and the full schematics for the ADM.)
Unlikely that the transformer changes the frequency - more likely that the terminal runs at 60Hz - this would not be unusual and is unrelated to the mains supply frequency

Rgds
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Old 22nd Jan 2020, 11:57 pm   #26
Greycon
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Default Re: 12" P4 Phospher CRT

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Originally Posted by kan_turk View Post
Quote:
Originally Posted by Greycon View Post
@linescan87 @dragonser I am using a decent 220V to 115V stepdown transformer unit. I changed the linesync DIP in the terminal switch to 50Hz and the cursor started rolling up the screen, so I assume the stepdown transformer unit changes the line frequency to 60hz, but I will check that later.

I can live with it, it's pretty minor, but I'm just curious as to how I might debug it. (I have a good scope and the full schematics for the ADM.)
Unlikely that the transformer changes the frequency - more likely that the terminal runs at 60Hz - this would not be unusual and is unrelated to the mains supply frequency

Rgds
John
OK, it's that there is a DIP switch inside the terminal that has to be set to either 60Hz or 50Hz, and the manual says to set it to match the line frequency. I am hoping to get back to playing with on on Friday
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Old 23rd Jan 2020, 5:58 am   #27
TonyDuell
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Default Re: 12" P4 Phospher CRT

Most likely that DIP switch changes the digital side of things so that the vertical frequency produced by the logic board is either 50Hz or 60Hz. It won't affect the analogue circuitry on the video monitor PCB which will have to lock to that. So it may just be a matter of tweaking the vertical hold preset on that board so that the picture locks in the 50Hz setting.

That said, there is no harm in running it set to 60Hz in the UK. The only possible issues are a hum bar on the screen if the PSU is not properly smoothed (but it should be!) or a flicker between the screen display and normal electric lighting. If you don't get these problems you don't _need_ to reset the switch.
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